Method of recovering silver and paper from silver-coated paper film

Abstract

A process for recovery of silver from silver-containing photographic emulsion-coated films, particularly films with paper or polymeric substrates. The process includes immersing photographic silver emulsion coated substrates, particularly paper, in a water-based solution of sodium hydroxide and sodium borohydride, with sufficient presence of an alkali metal hydroxide to maintain the solution at a pH of 11.0 to 12.0. Silver-containing emulsion layers are stripped from the substrate, while gelatin and other adhesive layers are dissolved. Silver present in a silver halide form is reduced to form metallic silver. The silver-laden emulsion is then treated using a polyamine coagulant and flocculant to induce precipitation of solids, particularly metallic silver, out of the solution. The exposure time of the paper to the wash bath is carefully controlled to permit recovery of the paper substrate.

What is claimed is: 
     
       1. A method for recovering silver and paper from silver-coated paper substrates, comprising:
 shredding silver-coated paper materials into silver-coated paper fragments; 
 transferring the silver-coated paper fragments into wash baskets; 
 immersing the wash baskets and silver-coated paper fragments into an alkaline wash solution, whereby silver is separated from the paper fragments, forming a silver-bearing emulsion solution; 
 removing the paper fragments from said wash solution and from said wash baskets; 
 rinsing the paper fragments with water; 
 recycling the rinsed paper fragments; and 
 treating the silver-bearing emulsion solution with a polyamine coagulant and flocculent to produce silver precipitate. 
 
     
     
       2. The method of  claim 1  comprising the further steps of:
 filter-pressing the silver precipitate to produce silver cake; 
 reducing the silver cake to ash by burning off carbonaceous content; and 
 smelting the ash to recover silver. 
 
     
     
       3. The method of  claim 2  wherein the alkaline wash solution contains sodim hydroxide and sodium borohydride. 
     
     
       4. The method of  claim 3  wherein the silver-coated paper fragments are immersed in the alkaline wash solution for between 10 and 15 minutes. 
     
     
       5. The method of  claim 2  wherein the alkaline wash solution is heated to between 170 and 180 degrees Farenheit during the wash. 
     
     
       6. The method of  claim 2  wherein the silver-coated paper fragments are immersed in the alkaline wash solution for between 10 and 15 minutes. 
     
     
       7. The method of  claim 1  wherein the alkaline wash solution is heated to between 170 and 180 degrees Farenheit during the wash. 
     
     
       8. The method of  claim 1  wherein the alkaline wash solution contains sodim hydroxide and sodium borohydride.